American Agriculture in the Twentieth Century:
How it Flourished and What it Cost

Bruce L. Gardner

American Agriculture in the Twentieth Century is not a general history
of United States agriculture, but a presentation of agroeconomic data.
This is obviously somewhat dry, but Gardner does a good job of making it
accessible, using graphs and diagrams to good effect, largely avoiding
mathematics or econometrics, and connecting the data to broader aspects
of agriculture.

Gardner begins with technology and productivity improvements, using the
introduction of tractors and hybrid corn as case studies. He covers
changes in farm numbers and sizes, and in farm incomes and distribution.
And he considers broader aspects of farm communities, such as age
distribution, schooling, out-migration and off-farm work, integration
with towns, and quality of life.

A long chapter on markets focuses on commodities but also considers
markets in inputs, in credit and labor. Two chapters explore the
role of government: the first covering infrastructure, loan subsidies,
and agricultural research and the second commodity prices, subsidies,
stockpiling, and insurance.

Looking for explanations, Gardner surveys the different attempts to
explain the standout feature of all this data, the rise in productivity
and output that started between 1935 and 1940 and has continued pretty
much since. These theories invoke research and education, the New Deal
programs, specialisation and scale, and other factors.

"It is unlikely that any one of the causal factors that have been
considered can qualify as the explanation for the takeoff in
productivity, or for the longer-term history of technological
change in U.S. agriculture."

Moving beyond case studies and narrowly restricted analysis to a
"systematic statistical investigation of interactions among the
hypothetically related variables" has not been possible, as "the time
series data are too dominated by trends, with a few structural changes,
that result in too few independent annual observations to identify the
relationships among them".

So Gardner turns to state and county level data, focusing on the same
trends, the growth in productivity and output and the growth in household
income. The data here still do not allow "a definitive contest between
different rival hypotheses for the acceleration of productivity growth
in the late 1930s". Nor do they provide a definitive evaluation of the
effects of commodity programs. But the growth of farm incomes is more
amenable to explanation:

"the most important factors in the growth of farmers' incomes
are not specifically agricultural at all. They key is rather
the economic adjustments of farm people to the opportunities
afforded by the nonfarm economy."

What little technical apparatus Gardner uses is explained as he goes.
So the first chapter considers the problems of constructing aggregate
indices, the choice of end-point, and related issues, and includes a
numerical worked example. The idea of a deadweight loss is explained
in the chapter on government commodity subsidies. And so forth. One
exception to this is that Gardner makes no attempt to explain regressions,
which get a workout in the chapters analysing state and county level data.

The data are linked to social history and politics, but only
superficially. And Gardner only touches narrowly on environmental costs,
with nothing at all about greenhouse emissions, to take one topical
example. But the biggest limitation is perhaps the restriction to those
topics where good time series data is available, either throughout the
20th century or in some cases for its second half.

By avoiding technical details, American Agriculture in the Twentieth
Century may frustrate economists. Its narrow focus may limit its appeal
to students or historians of agriculture, but it will be ideal for those
wondering what can be done with the long time scale quantitative data.